This invention relates to a precast concrete, dual wall smokestack constructed by stacking preassembled sections one upon the other.
Dual wall smokestacks have, in recent years, been widely used because the outer wall can be constructed of different material than the inner wall. Thus, the inner wall may be constructed of material best suited for transporting hot gases and the outer wall can be constructed of material best suited to support the stack both statically and dynamically. Furthermore, the gap between the inner wall and the outer wall may be filled with insulation to insulate the inner wall from the outer wall or the gap may be left as an air space which also provides insulation. This enables the inner stack temperature to be maintained during operation at a high temperature relative to the outer shell. This high temperature tends to reduce buildup of detrimental material on the inner surface of the inner wall and at the same time aids in the plume rise.
Dual wall smokestacks commonly have been constructed of steel. For example, a dual wall smokestack constructed of sections stacked one upon the other is described in U.S. Pat. No. 3,302,599. Each section of this smokestack has the air space between the inner and outer walls hermetically sealed. A non-sectionalized dual wall steel smokestack having freestanding inner and outer walls is described in U.S. Pat. No. 3,537,411. However, because of the high cost of steel in recent years, attention has been drawn to concrete stacks which in some instances are less expensive to build. Further, concrete stacks have asthetic possibilities which were not feasible with steel stacks.
Concrete stacks, because of their inherent weight, are generally constructed at the job site either by pouring the concrete stack directly or by constructing the stack with precast concrete sections.
U.S. Pat. No. 4,104,868 describes one such sectionalized precast concrete stack. This patent describes a method of constructing a chimney by stacking interfitting segments vertically to form an inner liner and then constructing an outer wall spaced from the inner lining by stacking interfitting segments vertically and in surrounding relation to the inner liner. The stack is built in sections. Reinforcing steel bars are placed in the interstitial gap between the inner liner and the outer wall during construction of the stack and concrete is poured in situ into the gap to cement the adjacent segments together. The inner wall in this smokestack is cemented to the outer wall.
West German Patentschrift No. 21 00 429 is also describes a concrete stack to be constructed in sections. This patent discloses preassembled sections to be taken to the job site having both an inner liner and an outer wall. During construction, the sections are placed one on top the other and morter placed between the sections to cement adjacent sections together. The sections are each carried to the job site in the preassembled state with a spreader bar having bolts threaded into threaded sleeves embedded in the inner liner and the outer wall. At the construction site, the bolts are loosened to permit relative displacement of the inner liner with the outer wall so that in the finally constructed stack, the joints between the inner liner sections and the outer wall so that in the finally constructed stack, the joints between the inner liner sections and the outer wall sections are staggered.